1. Field of the Invention
The present invention relates to a layer-by-layer etching apparatus using a neutral beam and an etching method using the same, and more particularly, to an etching apparatus having a neutral beam generator for easily generating a neutral beam and a layer-by-layer etching method using a neutral beam which enables to attain the precise control of etching depth and minimization of etching damage by etching layers to be etched in a layer-by-layer manner under proper control of acceleration energy of the neutral beam.
2. Description of the Related Art
As an increase in the integration density of semiconductor devices has been required, the design rule of integrated semiconductor circuits has been reduced. Thus, a critical dimension of 0.25 μm or less is needed. Ion enhanced etching tools, such as a high density plasma etcher and a reactive ion etcher are mainly used as etching tools for realizing nanoscale semiconductor devices. In such case, high density ions having energies of a few hundred eV bombard a semiconductor substrate or a specific material layer on the semiconductor substrate for anisotropic etching. The bombardment of such ions causes physical and electrical damages to the semiconductor substrate or the specific material layer.
Examples of physical damage are as follows. A substrate or a specific material layer having crystallinity is transformed into an amorphous layer. Also, a specific material layer, on which some incident ions are adsorbed or bombarded, of which partial components are only selectively desorbed therefrom to change chemical composition of a surface layer to be etched. Atomic bonds of the surface layer are changed into dangling bonds by this bombardment. Dangling bonds may result in electrical damage as well as physical damage. As electrical damage, there is gate dielectric charge-up or polysilicon notching due to photoresist charging. Besides this physical and electrical damages, there is also possible contamination by materials of a chamber or the contamination of a surface layer by a reactive gas such as the generation of C-F polymers caused by the use of a CF-based gas.
Physical and electrical damages due to the bombardment of ions reduces the reliability of nanoscale semiconductor devices and productivity. New apparatuses and methods for etching semiconductor devices are required to be developed in order to cope with the trend toward further increases in the integration density of semiconductor devices and reductions in design rule due to increased integration density.
An argon ion beam was conventionally used to etch an oxide, a nitride, and a carbide having excellent anticorrosion or in processing a thin film to an accurate and precise etching depth. In particular, the argon ion beam was necessary for a copper-based oxide reactive to a solution or the etching of ceramic thin films strongly resistive to acid.
However, the state of the argon ion beam may greatly vary depending on degree of vacuum in a vacuum apparatus and kinds of materials to be etched as well as voltage, current, and flow rate of argon gas controlled by an ion beam power supply. Thus, it is very difficult to repeatedly form an ion beam and the state of the ion beam continuously varies during its use. As a result, it is very difficult to repeatedly form etch patterns having a desired etch depth.
Also, a conventional ion beam etcher irradiates an etching gas and an ion beam or plasma at the same time on a material to be etched such as a silicon substrate such that it is difficult to precisely control the depth to be etched to an atomic level.
Thus, an etching apparatus and an etching method which are capable of reducing damage to a material layer to be etched by an ion beam under precise control of etching depth should be studied.